The subject matter disclosed herein relates generally to dryers and, more specifically, to systems and methods for determining a status of a drying cycle and for controlling a dryer.
Appliances for drying articles, such as laundry dryers or other machines for removing moisture (or other substances) from articles, typically comprises a cabinet containing a rotating container for tumbling the articles therein. A blower provides a stream of air for circulating through the articles in the container. One or more heating elements increases the temperature of the incoming air prior to its introduction to the container, causing the incoming air to carry a relatively low level of humidity. The warm, relatively dry air is circulated through the container as it tumbles the articles, decreasing the water content therein while increasing the relative humidity of the circulating air. The humidified air is then exhausted from the container and replaced with more heated, relatively dry air, whereby moisture is effectively removed from the articles in the container.
At least one known laundry dryer utilizes an open loop control system to determine an appropriate amount of time for drying a load of laundry. In this common system, an operator selects a desired drying time using a manual control, such as a time selector knob. For the duration of the selected drying time, the container is rotated, a blower removes air from the container, and heating elements add heat to produce a stream of warm, dry air entering the container. As long as moisture remains in the articles in the container, moisture is available for uptake by the circulating air, and the exhaust air will carry more humidity than the incoming air. When the articles in the container have released most or all of their available moisture, the circulation of warm, dry air inside the container will remain warm and dry, and the exhaust air will also be warm and dry. Absent means for detecting the completion of the goal of drying the articles, the open loop control system will continue to operate the laundry dryer until the prescribed period of time has elapsed. In some cases, this period of time is insufficient to remove all of the excess moisture from the articles. In other situations, the period of time may be too long and the articles dried more than the user desires.
Moreover, these drawbacks are not limited to laundry dryers; they also occur in systems for removing moisture from articles other than laundry articles. Still further, they occur in systems for removing substances other than water (e.g., alcohol, naphthalene, turpentine, dry-cleaning fluid, solvents, or other substances) from articles to be “dried”.
Based on the foregoing, those skilled in the art seek improved systems and methods for determining a status of a drying cycle and for controlling a dryer.